Half of Britain's motorists have no idea how much their vehicle depreciates by each month, according to a new report by CAP Automotive.
A typical medium-sized family car falls in value by more than £300 every month – more than most household bills.
However, of 500 motorists quizzed by CAP, 48% had no clue about this until the time came to sell.
A new free Total Cost of Motoring tool on the CAP website reveals the stark differences between similar cars.
For example, the difference over three years between the total cost of owning the cheapest and the most expensive supermini registered in October 2013 is predicted to be a whopping £8,783.
Philip Nothard, retail & consumer pricing expert at CAP, said: “Our research shows that depreciation is the one area where people are still in the dark – even though it is the cost that hurts them most.
“The Total Cost of Motoring tool gives everyone a chance to make the best choice to suit their long-range budget.”